Divine Defiance( Fiendish Codex II: Tyrants of the Nine Hells, p. 83)
You can channel divine energy to counter spells without readying an action in advance.
Divine caster level 3, Ability to turn or rebuke undead,
You can spend one of your turn or rebuke undead attempts as an immediate action to counter a spell or spelllike effect. For example, if an evil cleric targets Jozan with a hold person spell, as an immediate action, Jozan can spend a turn undead attempt to counter the spell if he had prepared a hold person or dispel magic spell. You must have the relevant spell prepared as normal (or dispel magic), and you must make a Spellcraft check to identify the target's spell if applicable. (See PH 170 for details on counterspells.)
You must typically use a readied action to counter an enemy's spell.